Familial Hyperlipoproteinemias (Types I – V)
| Type & Name | Inheritance / Defect | Elevated Blood Lipids | Key Clinical Findings & Complications |
|---|---|---|---|
| Type I Hyperchylomicronemia |
Autosomal Recessive LPL or Apo C-II deficiency |
Chylomicrons Triglycerides > 1000 mg/dL |
Acute pancreatitis, eruptive xanthomas, hepatosplenomegaly, lipemia retinalis. No increased risk for atherosclerosis. Creamy layer on top of plasma. |
| Type IIa Hypercholesterolemia |
Autosomal Dominant Defective or absent LDL Receptor |
LDL Cholesterol (~300-1000 mg/dL) |
Severe premature coronary artery disease, tendon xanthomas (Achilles), and corneal arcus. Homozygotes can have MI before age 20. |
| Type IIb Combined Hyperlipidemia |
Autosomal Dominant Decreased LDL-R and increased Apo B-100 |
LDL and VLDL Cholesterol & Triglycerides |
Highly atherogenic. Strongly clustered with metabolic syndrome, insulin resistance, and premature cardiovascular disease. No hay tendón xantomas. |
| Type III Dysbetalipoproteinemia |
Autosomal Recessive Homozygous for mutant Apo E2 |
Chylomicron remnants & IDL | Palmar xanthomas (yellow creases on hands), tuberoeruptive xanthomas (elbows/knees), and premature peripheral vascular and coronary disease. |
| Type IV Hypertriglyceridemia |
Autosomal Dominant Hepatic overproduction of VLDL |
VLDL Triglycerides (~200-500 mg/dL) |
Increased risk of cardiovascular disease. Frequently associated with type 2 diabetes mellitus, obesity, alcohol use, and insulin resistance. |
| Type V Mixed Hypertriglyceridemia |
Complex/Multifactorial Increased VLDL production + decreased LPL |
VLDL and Chylomicrons | Elevated risk for acute pancreatitis, eruptive xanthomas, and severe insulin resistance. Turbid/milky plasma with a distinct creamy top layer. |
High-Yield Differential Distinctions:
- The Pancreatitis vs. Atherosclerosis Split: Severe elevations in triglycerides (Types I and V) trigger mechanical capillary plugging by large chylomicrons/VLDL in the pancreas, releasing toxic free fatty acids that cause acute pancreatitis. Isolated LDL elevation (Type IIa) causes macrophage foam cell accumulation inside vessel walls, steering purely toward accelerated atherosclerosis.
- The Isoform Trap (Type III): Normal Apo E3 and E4 bind tightly to hepatic remnant receptors. The Apo E2 variant has an altered structural charge that reduces its receptor binding affinity to less than 1%. This leaves chylomicron remnants and IDL floating in circulation, building up pathognomonic lesions in the palmar creases.
- The Refrigerator Plasma Visual Test: Drawing blood and letting it sit overnight distinguishes lipid mechanics. Type I forms a clear, creamy layer floating at the top of an otherwise translucent plasma base (pure chylomicrons). Type IV shows uniformly turbid, milky plasma throughout (pure VLDL). Type V exhibits a thick creamy top layer resting on an underlying turbid, milky column (both chylomicrons and VLDL present).